Microsoft explains why Visual Studio 2010 design is a bit different from the Windows 7 design:

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While the Visual Studio 2010 visual appearance is unique, it does follow the Microsoft Windows UX guidelines. Microsoft does not use one standard visual appearance for all its products for multiple reasons, including:

• Not every product has the same users and thereforethe same UI is not appropriate everywhere [!] • Microsoft has such a wide range of products, it would be impossible to do one visual appearance that is a "one size fits all." For example, it would be virtually impossible to use a single UI design for Zune, XBox, Visual Studio and Bing. [!!]• Different visual appearance of different products helps differentiate/brand them. [!!!]• Having a single UI appearance would not give individual products flexibility to evolve as needed in response to trends, customer and business needs.[!!!!!]

Microsoft doesn't have one visual appearance across all its products now either. "Metro" isn't really a single visual style, it's more like a family of styles - Windows Phone "Metro" is different from Windows 8 "Metro" is different from Office "Metro" is different from VS2012 "Metro", etc. As for Windows 8 on various form factors, it's not a case of the same UI across multiple products as Windows 8 is a single product (whether you think it should be or not).